I also have same problem after upgrading. I had this problem few times before after upgrade from 2.3.x. Before I just made restore of site from backup when site was OK, but it's so dull if I must do this almost every month.
So, I can't login, actually if I try to login xoops said everithing is ok with login but my path to web site is something like this:



but it sould be onlyhttp://1os-petrinja.hr

After that if I try to go to admin side it said I don't have rights to go there and then I'm again logout.

If I try to open user.php I get blank page.

What should I do?

Thanks in advance

Hmm it looks there is problem with my language files (croatian). I changed to english from phpmyadmin and it works now. I'm confused because everithing worked ok when I made upgrade to 2.5.0, and few days after that.